CF455A.Boredom

Alex doesn't like boredom. That's why whenever he gets bored, he comes up with games. One long winter evening he came up with a game and decided to play it.

Given a sequence a consisting of n integers. The player can make several steps. In a single step he can choose an element of the sequence (let's denote it a__k) and delete it, at that all elements equal to a__k + 1 and a__k - 1 also must be deleted from the sequence. That step brings a__k points to the player.

Alex is a perfectionist, so he decided to get as many points as possible. Help him.

亚历克斯不喜欢无聊。因此，每当他感到无聊时，就会想出一些游戏来玩。在一个漫长的冬夜，他想出了一个游戏，并决定开始玩。

给定一个由 $n$ 个整数组成的序列 $a$。玩家可以进行若干步操作。在单步操作中，他可以选择序列中的一个元素（记为 $a_k$）并将其删除；此时，序列中所有等于 $a_k + 1$ 和 $a_k - 1$ 的元素也必须一并删除。该步操作为玩家赢得 $a_k$ 分。

亚历克斯是个完美主义者，因此他希望获得尽可能多的分数。请帮助他。

The first line contains integer n (1 ≤ n ≤ 105) that shows how many numbers are in Alex's sequence.

The second line contains n integers _a_1, _a_2, ..., a__n (1 ≤ a__i ≤ 105).

第一行包含一个整数 $n$（$1 \leq n \leq 10^5$），表示 Alex 序列中数字的个数。

第二行包含 $n$ 个整数 $a_1, a_2, \ldots, a_n$（$1 \leq a_i \leq 10^5$）。

Print a single integer — the maximum number of points that Alex can earn.

输出一个整数——Alex 能获得的最高分数。

Consider the third test example. At first step we need to choose any element equal to 2. After that step our sequence looks like this [2, 2, 2, 2]. Then we do 4 steps, on each step we choose any element equals to 2. In total we earn 10 points.

考虑第三个测试样例。第一步，我们需要选择任意一个等于 2 的元素。完成该步后，序列变为

$$2,\,2,\,2,\,2$$

接着我们进行 4 步操作，每步均选择任意一个等于 2 的元素。总共获得 10 分。